Scientists Sound Alarm on State of the World’s Rivers

Today, a team of international scientists published the first ever global review of human impacts (such as pollution, dam building and agriculture) on the world’s rivers. Their findings are not pretty: Rivers that serve nearly 80 percent of the world’s population suffer from serious threats to human water security and biodiversity. In spite of billions of dollars in investment, the threats to river ecosystems are particularly high in Europe and the United States. The good news is that smart and cost-effective solutions are available.

The global review was led by professors Charles Vörösmarty and Peter McIntyre, in cooperation with scientists from the United States, Australia, Switzerland and Hong Kong. The authors analyzed 23 different stress factors and merged them into two cumulative indices, one for human water security and one for biodiversity. Their review, which was just published in the journal Nature, constitutes the first systematic effort to account for human resource use and the protection of ecosystems in the water sector.

Through their research, the scientists discovered “a global syndrome of river degradation,” which poses major problems to human water security and biodiversity. They found that 4.8 billion people – nearly 80 percent of the world’s population – live in areas with grave threats to human water security or riverine biodiversity. This includes much of the United States and Europe and large portions of central Asia, the Middle East, the Indian subcontinent and eastern China. (See the maps below.)

Threats to river biodiversity and human water security

Nature

The scientists also found that 65 percent of the world’s river discharge is under moderate to high threat of biodiversity loss. Estimates suggest that at least 10,000-20,000 freshwater species are already extinct or at risk.

As the figure below indicates, water resource development and pollution are the main threats to human water security and biodiversity. Under the rubric of water resource development, dam building and river fragmentation are the main factors threatening biodiversity, while water abstraction is the main threat to human water security.

So far, industrialized countries have relied on expensive technical fixes to treat the symptoms of river degradation rather than protecting the resources. The authors find that this approach “does little to abate the underlying threats, producing a false sense of security in industrialized nations and perilous water insecurity in the developing world.”

Factors of water stress

Nature

Developing countries won’t be able to afford the industrialized world’s approach – and there are better ways. The scientists’ take-home message is that “it is more cost effective to ensure that river systems are not impaired” than to offset threats once they arise. The concept of integrated water resource management – including dam operating rules that integrate economic and ecological objectives, the protection of catchment areas and the preservation of floodplains – offers such a preventive approach.

The authors state:

"In populated regions of the developed world, existing human water security infrastructure will require re-engineering to protect biodiversity while retaining human water services. Across the developing world, establishing human water security for the first time while preserving biodiversity constitutes a dual challenge, best met through integrated water resource management that expressly balances the needs of humans and nature.”

Peter McIntyre, a zoologist at the University of Madison and one of the review’s lead authors, comments:

“The hard lessons learned by the developed world can help governments and planners in other parts of the world avoid making the same mistakes and experiment with new strategies for promoting water security and protecting biodiversity. Instead of investing billions of dollars in expensive remediation technologies, strategies such as protecting watersheds, for example, can reduce the costs of drinking water treatment, preserve floodplains for flood protection and enhance rural livelihoods.”

Powerful institutions, including the World Bank, continue to advise developing countries to follow the industrialized world’s expensive, engineering-first approach to water sector development. The Nature study shows empirically that protecting biodiversity is a more cost-effective way to address water needs than the traditional engineering approach.